1. Field of the Invention
The present invention relates generally to control of a power amplifier, and more particularly, to a device and method for controlling a power amplifier bias applied to a power amplifier according to a communication environment.
2. Description of the Related Art
An electronic device may implement a wireless communication function by receiving or transmitting signals using an antenna included in the electronic device. The antenna is able to efficiently restore an original signal from a signal detected from a free space using a filtering function and amplification (e.g., low noise amplification) function, even if the strength of the detected signal is low. However, when the antenna transmits a signal through free space to an entity a great distance from the electronic device (e.g., another terminal, a base station, or a network), the electronic device must sufficiently amplify transmission power (e.g., power amplification) in order to deliver the signal. In order to enable transmission over greater distances, the electronic device uses a Power Amplifier (PA) to amplify power at a transmitting end. The PA may be operated using specified Direct Current (DC) power, i.e., a bias voltage, as a power source.
In a power amplifier control method according to the related art, the same PA bias value is applied to a frequency band (e.g., 1920 MHz to 1980 MHz for an uplink, 2110 MHz to 2170 MHz for a downlink, 2×60 MHz band in total) corresponding to one RF band (e.g., band 1 of WCDMA), in order to reduce power consumption of a power amplifier.
However, according to this power amplifier control method, since a low bias value may be applied even to some channels having a poor PA linearity, such as an Adjacent Channel Leakage Ratio (ACLR) among a plurality of channels existing within one band, reception sensitivity degradation may occur due to transmission. Furthermore, since the same bias value is used for both data communication and a voice call, a bias value for optimizing current consumption for the voice call may also be used for the data communication. As a result, according to the power amplifier method according to the related art, performance degradation may occur in a data mode for which a greater ACLR performance is required.
In contrast to a typical LTE terminal, a terminal that supports Carrier Aggregation (CA) of LTE-Advanced (LTE-A) technology may be additionally provided with a wideband coupler, or an antenna switch and a diplexer, for separating high and low bands between an antenna and a duplexer. Due to such additional elements, a transmission path loss may be increased by 1 dB to 3 dB in an electronic device that supports the CA. To compensate for this loss, the terminal must increase an output of a voltage amplifier by 1 dB, so that current consumption of the voltage amplifier increases. For example, if a maximum transmission power is increased by 1 dB to 3 dB, the terminal consumes as much as several tens or several hundreds of milliampere of additional current, thereby degrading the PA linearity.